Carbon nanotubes and their application to very long span bridges

Abstract

Spanning long distances in bridge construction relies mainly on the structure's efficiency and materials used. Whereas structural design for high rise building is fast-expanding, the overall design of long span bridges has not progressed significantly, and the increase in span chiefly depends of new materials. Carbon nanotubes, with their extraordinary Young's modulus and tensile strength far exceeding steel, allow the production of ultra-strong cables which can be used for cable- based structures like suspension bridges. However, since nanoscopic elements are used to produce kilometer-long cables, it is difficult to calculate their real strength, taking into account physical and production defects. This thesis provides the background necessary to understand the complexities involved in creating a kilometer-long cable made of carbon nanotubes. It also presents a computer program that computes the theoretical tensile strength of such a cable for a given set of assumptions about nanotubes. Scenarios varying the mechanical properties (tensile strength and Young's modulus) are applied to a cable-stayed and a suspension bridge, and it is shown than spans longer than five kilometers could be realized with such technology.